Not knowing where we are makes us all a little crazy. Consider how you feel when you’re driving along a strange road without a map or a GPS. Consider how you feel when you’re on the street in a city overseas, having no idea how to get back to your hotel and you don’t speak the local language. There’s a reason people freaked out when Apple dropped Google Maps. There’s a reason airplane seatbacks have little route maps on the screen. It takes a solid sense of place, it seems, to give us a solid sense of safety.

So pity the scientists tracking the Voyager 1 spacecraft.

As most people who pay attention to these things noticed yesterday, there was a cosmic battle royal when the American Geophysical Union (AGU) issued a surprise press release about new Voyager readings with the stunning headline: “Voyager 1 has left the solar system, sudden changes in cosmic rays indicate,” making it the first human-built object to cross that remarkable threshold. But NASA, which knows a thing or two about the twin Voyager spacecraft since it built them, launched them and controls them, fired back with a press release that said, in effect: Not. The NASA release tersely quoted the venerable Ed Stone, who has been at the helm of the Voyagers since the start of the program in 1972:

“The Voyager team is aware of reports today that NASA’s Voyager 1 has left the solar system,” said Edward Stone, Voyager project scientist based at the California Institute of Technology, Pasadena, Calif. “It is the consensus of the Voyager science team that Voyager 1 has not yet left the solar system or reached interstellar space.”

The AGU, to its credit, responded within minutes, reissuing the same press release with details of the findings unchanged, but with a more cautious headline: “CORRECTED — Voyager 1 has entered a new region of space, sudden changes in cosmic rays indicate” [emphasis added]. So, good for the AGU: it conducted a solid study, got called for a little too much breathlessness and stepped back. “It’s a matter of interpretation,” says Peter Weiss, AGU public-information manager. “We were trying to write it in a way that people would understand, so maybe we did get a little overzealous in our headline writing.”

That led to the usual schadenfreude in certain circles, the look-who-screwed-up snickering that always comes when a lab or a government or a politician has to walk back a statement. But the fact is, in this case, nobody misspoke, nobody got it wrong. Weiss is right when he says these things are a matter of interpretation — and that’s one of the reasons they’re so bloody much fun.

This isn’t the first time we’ve tried to determine if or when one of our little machines left the solar system. TIME said we did it in 1983, and before you direct those snickers our way, the scientific community was in complete accord on the matter. That time the spacecraft was Pioneer 10, and what it had done to achieve the landmark feat was cross the orbit of Neptune. Since the elliptical orbit of Pluto (which was a planet then but is no more) at that point took it inside the orbit of Neptune, Pioneer 10 had indeed passed the last recognized toll booth to the unknown.

But here’s the thing: at the time, Pioneer 10 was just 2.8 billion miles (4.5 billion km) away, and Voyager 1 — now 11 billion miles (18 billion km) distant — has nearly quadrupled that stretch. What changed is our subjective definition of where the exit door lies.

No longer do we define the solar system the way we define the highways around Beijing — with inner, middle and outer rings, all firmly circumscribed. In the same way the sprawl and the smog of Beijing reach far outside the city limits, so too does the solar system make its presence felt beyond the orbit of its last big world, thanks to the heliosphere, a vast gale of charged particles streaming forth from the sun and extending perhaps 12 billion miles (19 billion km) in all directions. Only when the solar wind becomes so attenuated that the outward flowing particles bump up against the higher energy particles of interstellar space do we now consider the solar system at an end. When you change how you draw the map, you entirely upend the sense of where — and even then there is some confusion.

In the summer of 2012, the solar wind surrounding Voyager 1 came to a dead stop, a boundary known as the heliopause, and by some definitions that should have been it, the ship should have been out. And then, capriciously, it just started up again. NASA and the AGU agree that the end game will truly be upon us when the wind stops for good and Voyager punches through the so-called heliosheath, when outward-flowing energy drops to effectively zero and inward-flowing interstellar energy spikes. Those findings were confirmed by the study the AGU released yesterday, leading to the somewhat premature announcement.

But NASA adds another condition — one that the AGU accepts: the magnetic field that surrounds the ship will have to change direction, indicating that solar magnetism is yielding to the deeper magnetism of space. Last December, the fields began interlocking and lining up — putting Voyager on what Stone calls the magnetic highway. But the ship hasn’t taken the exit ramp to deeper space yet. “A change in the direction of the magnetic field is the last critical indicator of reaching interstellar space and that change of direction has not yet been observed,” he said in the NASA release.

Before long, on the order perhaps of months, that will happen — the scientific interpretations will line up as neatly as the magnetic fields and everyone will agree that yes, Voyager 1, first a thing of the earth, then a thing of the local solar system, has well and truly become a thing of the stars. For now, let’s abide — and even enjoy — the uncertainty. On some journeys, the best answer to the question “Where are we?” is a simple “Beats the hell out of me.”

Great article and many, many excellent comments in the mind of this very fascinated yet admittedly novice student of space exploration, science and physics.

Having said this, one thing I found remarkable as I read through the article and comments -- and I wonder if others might agree -- is that during its amazing journey Voyager I has not run into (or been run into), and destroyed, by something.

Sir Issac Newton says you are wrong ! There is no "gravity" between the stars - Newton's formula makes that very clear - but what you can measure - is the electromagnetic waves of plasma particles - That is the "force" that connects everything !

good to see that there is no consensus among the scientists themselves. For sure, this will put more concern and emphasis on the science community to really verify and then come to conclusion. After all, we all are trying to understand something new, and if it will be great if there are valid consensus too !

Personally, I think the boundary of the solar system is at the edge of the sun's gravity well. That consists of all those nearest locations where if an object is placed at rest with respect to the sun it would not fall back towards the sun but eventually drift away instead. I am not an astronomer and I don't know if Voyager 1 has gotten that far yet but if it hasn't I expect it will (again) be declared to have left the solar system when it does.

Not to be a Debbie Downer, in fact I think this should be UP-lifting, but if a starship existed, it would have covered this tiny distance in less than a second. Voyager, however, is moving at around 40,000 miles per hour, or in other words, 0 miles per hour. STAR ship? We've a long way to go so let's "MAKE IT SO!"(The first trick is to figure out how to go 1/10th light speed - Arthur C. Clarke brought up an excellent point that we don't know how to go that "fast," or rather, how to travel at that appallingly-slow speed. 18,628 miles per second takes more energy than we can really generate at-present and even if we can, the *heat* generated would melt the engines - plus there's "diminishing returns" - for example more nuclear energy would require heavier shielding but then you need to push more mass - similar problems with "Bussard ramscoops," ion engines etc. But the more we learn the closer we'll get to doing it so let's get movin! :)

When will Voyager reach the point where it is more strongly under the influence of the gravity of another star rather than the Sun? That is an exact, easily calculated point, though it is probably decades from now.

Well, if Voyager follows the same tracking patterns found here on earth, it will return back to earth in a few thousand years; provided the earth is not lost in space. Give me a break, this is one of those questions that will never be answered by HUMANS.... or, if you're Captain Kirk.

@majikI am no astrophysicist, but, I think "dark energy" might have a role in
this issue. Instead of galaxies/stars coming together due to gravity,
dark energy is propelling them apart, expanding our universe.

@dehinstodits Given that with sufficiently sensitive instruments, the gravity of any single star can theoretically be detected anywhere in the universe, I think you'll need to narrow down that range just a little bit.

@rameshConsensus comes from data. So far, we've never had any from that far out. The data isn't conclusive in its support of many assumptions and theories. Therefore there will be disagreement as to how the data we are getting will be interpreted.

Given the apparently fluid nature of the border of the heliosphere, which is what many scientists define as the "edge of the solar system", I expect that an average or range will have to be established to take into account variable solar activity which produce the charged particles that reach out into space. The more active the sun is, the more charged particles will be flung out there and the further away the solar system border is. The quieter solar activity is, the fewer charged particles are being flung out there, and the closer the border of the solar system is. Like pressure in a balloon, the more you have, the larger the balloon and the less you have the smaller.

This doesn't even take into account the fact that solar activity is vector based instead of spherical. Flares and CME's get thrown out along specific arcs, which for that region of the heliosphere extends the presence of charged particles. So the heliosphere, instead of a smooth, round sphere is in actuality a three dimensional blob of varying size and shape which can have up to several billion miles in difference between the "valleys" and the "peaks".

Defining a line in there saying "You are now leaving the solar system, please drive carefully" is where lies the confusion.

Continuous thrust can do the same thing without your problems.... generate 1G of continuous thrust for a year and you will be going pretty damn fast and without any such nonsense as engines melting nor would relativistic mass increase problematically until 30-50% light speed.

I think it must be more like centuries. At least, to get to the point where the general public would consider it a reasonable amount of "pull," as opposed to something ridiculously far away being measured by high-tech highly-sensitive instruments. It hasn't moved yet, it's still at Earth, or in other words, in the vicinity of Pluto. ;) Don't forget it's standing still, or to be fair, "moving" at 40,000 miles an hour.

@TimothyRigney My point was that we don't need to measure anything or worry about the general public. This is just a theoretical calculation. We only need to know the distances of Voyager to the Sun and to the next nearest star and the masses of those 2 objects (or the whole solar system to be more accurate). I assume they'll be only one star that it will bet near to. At 40,000 mph it is traveling about 350 million miles per year which is 0.035 trillion miles per century. Seeing as even the nearest star is about 24 trillion miles away, we've got a long wait.

@majik @DrTom Be careful when you use the word "no" as a mathematical concept. I think you mean "really, really small". As we travel toward another star we'll eventually reach a point where the gravitational force on us from the star and from our sun is exactly equal. On a much smaller scale the same thing happens between the earth and the moon as we travel from the earth to the moon; this is known as the neutral point and is about 239,000 miles from the earth. This is a theoretical point not taking into account that the earth and moon are orbiting each other.

@majik@DrTom I don't have a book in front of me, but last I checked, there are measurable gravitational effects between the largest structures in the observable universe - superclusters, etc. These things are way further apart than any two neighboring stars. What about any of Newton's equations denies the effect of gravity over long distances? Not sure what you're referring to.

@DrTom True; BUT .. the amount of "gravity" between our sun & the nearest star (Alpha-Centuri) is so tiny (d squared) it has no effect ! Newton proved that as FACT! Today's Science supports that same equation!